CLARK, JOSIAH LATIMER (1822–1898), English engineer and electrician, was born on the 10th of March 1822 at Great Marlow, Bucks. His first interest was in chemical manufacturing, but in 1848 he became assistant engineer at the Menai Straits bridge under his elder brother Edwin (1814–1894), the inventor of the Clark hydraulic lift graving dock. Two years later, when his brother was appointed engineer to the Electric Telegraph Company, he again acted as his assistant, and subsequently succeeded him as chief engineer. In 1854 he took out a patent “for conveying letters or parcels between places by the pressure of air and vacuum,” and later was concerned in the construction of a large pneumatic despatch tube between the general post office and Euston station, London. About the same period he was engaged in experimental researches on the propagation of the electric current in submarine cables, on which he published a pamphlet in 1855, and in 1859 he was a member of the committee which was appointed by the government to consider the numerous failures of submarine cable enterprises. Latimer Clark paid much attention to the subject of electrical measurement, and besides designing various improvements in method and apparatus and inventing the Clark standard cell, he took a leading part in the movement for the systematization of electrical standards, which was inaugurated by the paper which he and Sir C. T. Bright read on the question before the British Association in 1861. With Bright also he devised improvements in the insulation of submarine cables. In the later part of his life he was a member of several firms engaged in laying submarine cables, in manufacturing electrical appliances, and in hydraulic engineering. He died in London on the 30th of October 1898. Besides professional papers, he published an Elementary Treatise on Electrical Measurement (1868), together with two books on astronomical subjects, and a memoir of Sir W. F. Cooke.